The inventions presented herein relate to method and apparatus for the diverting of harmful electrical voltage and current disturbances on alternating current (xe2x80x9cACxe2x80x9d) power lines supplying power to portable personal computers, hereinafter referred to as xe2x80x9cnotebook computers,xe2x80x9d a xe2x80x9cnotebookxe2x80x9d or xe2x80x9cnotebooks.xe2x80x9d
Generally, manufacturers and/or re-sellers of notebook computers powered by a 16 volt direct current (xe2x80x9cdcxe2x80x9d) battery, for example, make available to their customers a power adapter to produce a 16 volt dc output from different rated alternating current (xe2x80x9cACxe2x80x9d) power services available from public or private electric power utility companies. For example, a power adapter generates the 16 volt de voltage to run a notebook from a 120 volt, 60 cycles per second (xe2x80x9ccpsxe2x80x9d) power service commonly available throughout the Untied States at a wall mounted outlet in most homes and places of business. In addition, the power adapter simultaneously re-charges the notebook""s battery. The power adapters also produce the required 16 volt dc voltage from AC power sources used in other countries of the world including: a 100 VAC. 50 cps, rated service used in Japan; and a 240 volt 50 cps rated service used in Europe, Asia, the Middle East, South America and Africa.
It is known among manufacturers of notebooks to locate a power adapter inside the housing of a notebook. For brevity, the following discussion is limited to power adapters which are external to the notebook housing. The housing for an external power adapter is generally rectangular in shape and about the size of a audio cassette tape. Characteristically, power adapters include both AC and dc power cords. The dc power cord is anchored at one end to the power adapter and has a female dc plug at a free end for mating with a male dc receptacle mounted in the notebook housing. The AC power cord is a removable, specialized, electrical extension cord. The AC power cord has a two wire female AC plug at one end for mating with a male AC receptacle mounted in the housing of the power adapter and a two wire male AC plug at its other end for coupling to an AC power service at a standard female AC receptacle, wall mounted, for example.
Detachable AC power cords are available from or through notebook manufacturers. These AC power cords include the required male AC plug needed to fit the unique configuration of a female AC power receptacle of the AC power utility of a given country or region of the world. Consequently, an international traveler is advised to bring as many AC power cords having country specific AC plugs as required for mating with the unique mating connector of each power utility encountered on a multi-country trip.
An additional consideration for notebook computer owners is an electrical surge protector for notebooks to protect their notebooks from harmful electrical disturbances such as voltage and current transients which can damage a notebook. A damaged notebook normally means the owner looses the use of the notebook for getting productive work done. Harmful electrical disturbances occur on AC power lines for several well-known reasons including switching ON or OFF an electric motor or a circuit breaker carrying large electrical currents. Lightening strikes of AC power lines during electrical storms are another well-known cause for harmful electrical disturbances appearing on AC power lines.
Protection of notebooks from the foregoing and other harmful electrical disturbances is a concern to users of notebook computers regardless of the country or utility district in which a notebook is operated. In the United States. Underwriters laboratories (xe2x80x9cULxe2x80x9d), an electrical product safety standard setting and testing organization, provides criteria for evaluating the performance of surge protectors, when coupled to a 120 VAC rated AC power service. Specifically, the UL 1449 standard sets forth: (1) a let-through voltage criteria and (2) an effective clamping voltage criteria. Each test criteria is useful for evaluating the performance of surge protector equipment intended to guard notebook computers from harmful electrical AC line disturbances.
A main component of prior art surge protectors for use with notebooks coupled to a 120 volt rated AC power service is a metal oxide varistor (xe2x80x9cMOVxe2x80x9d) or other voltage and current diverting and absorbing semiconductor devices, such as, transorbs and sidactors. A MOV is the diverting and absorbing semiconductor device used in the majority of prior art surge protectors to protect notebooks from harmful electrical disturbances. A typical prior art surge protector employs a single MOV in combination with a fuse to protect a notebook from harmful electrical disturbances.
Therefore, a first aspect of the present surge protector is to improve the performance of surge protectors for use with notebook computers by designing them to achieve an effective clamping voltage of 330 volt, while coupled to an AC power service rated from about 100 to about 120 volts, which is the best clamping voltage rating under the UL 1449 standard.
Accordingly, an important aspect of the present surge protector is to improve the level of protection for notebooks from harmful electrical disturbances over that achieved by prior art surge protector, while coupled to AC power services rated from about 100 to about 120 VAC which substantially achieves the UL 1449 standard 330 volt best clamping voltage and a low let-through voltage.
Another significant aspect of the present surge protector is the universal ability to protect a notebook from harmful electrical disturbances appearing on an AC power line in nearly every developed country and in many undeveloped countries, of the world.
Still another novel aspect of the present surge protector is that it employs two, differently rated, MOVs for protecting a notebook wherein a first, higher rated MOV protects a notebook while the surge protector is coupled to a high rated 240 VAC power service and a second, lower rated MOV protects the notebook while the surge protector is coupled to a lower rated AC power service of from about 100 to about 120 VAC.
Yet another aspect of this surge protector is that it includes a switch comprising a switching circuit which automatically connects a lower rated MOV across an AC power line when the AC power line is coupled to a lower rated AC power service and automatically disconnects the lower rated MOV from the AC power line when the AC power line is coupled to a higher voltage service leaving the higher rated MOV to protect a load, such as a notebook.
The present surge protector overcomes the limitations of existing surge protectors used with notebooks to the benefit of international travelers who carry notebooks along with them into countries having different rated AC power utilities. As pointed out above, an important aspect of the present surge protector is the ability to use a single surge protector unit to protect a notebook in multiple countries each having differently rated AC power services or, within one country having two or more differently rated AC power services. Specifically, the present surge protector is operable to protect notebooks when they are coupled to either a high rated AC voltage source, such as 240 VAC, 50 or 60 cps or a low rated AC voltage source such as a 100 or 120 VAC, 50 or 60 cps AC power service. The surge protector offers protection for notebooks while coupled to AC power services rated from about 70 VAC to about 290 VAC.
The ability to protect notebooks when coupled to variously rated AC power sources is achieved by organizing the surge protector into two parts or sections. A first section of the surge protector includes a first MOV for protecting a notebook from electrical disturbances appearing on an AC power line coupled to a 240 volt AC power service. A second section, coupled in parallel with the first section, includes a second MOV for protecting a notebook from electrical disturbances appearing on an AC power line coupled to an AC power service rated from 100 to 120 VAC. Consequently, the single surge protector described herein is usable, for example, successively in Japan, the United States and Canada which offer low AC power services rated at 100 and 120 VAC, respectively, and in various European, Asian, African and South American countries which offer high AC power services rated at 240 VAC.
Both sections of the present surge protector are automatically selected to protect a power adapter and associated notebook when the AC power line is coupled to a low rated AC power source, for example, a 120 VAC rated AC power service. Only the first section of the surge protector is selected to protect the power adapter and notebook when the AC power line is coupled to a high rated AC power service, for example, a 240 VAC rated power service. A switch within the second section of the surge protector includes an electrical-mechanical relay which automatically connects the second MOV across an AC power line when the line is coupled to a low rated AC power service and automatically disconnects the MOV from the AC power line when the line is coupled to a high rated AC power service.
The two MOVs, relay and other electrical components of the surge protector are mounted on a printed circuit board (xe2x80x9cPCBxe2x80x9d) and are coupled to one another by, conductive tracings on the PCB. The particulars of the surge protector circuits are given below.
The surge protector disclosed herein is contained in a small housing large enough to hold the above-described PCB and all the components carried by the PCB further including a male AC receptacle for mating with a female AC plug at one end of an AC power cord. Under normal operating conditions, the housing is not noticeably warm to the touch when the surge protector is coupled to AC power services rated form 100 to 240 VAC.